Understand the monitoring tools at hand. Do you have, or do you plan to run, a full-fledged NMS? Or do you plan to develop your own standalone monitoring tools? Does your directory server software support SNMP?
Ensure that any custom-built monitoring tools simulate actual directory operations.
Decide what will be considered a failure of the directory. Set acceptable performance levels, taking into account any service-level agreements that may be in place.
Implement log file analysis.
Implement OS performance data analysis.
Implement indirect monitoring.
Decide on a notification strategy, implement notification methods , and develop a test plan for them.
When an incident occurs, keep detailed records and use the knowledge gained while resolving the problem to improve the quality of your directory service.
Understanding and Deploying LDAP Directory Services, 2002 New Riders Publishing